refactor: log dynamic-theme initialization

src/main/java/com/flowingcode/vaadin/addons/demo/DynamicThemeInitializer.java

@@ -5,7 +5,12 @@
 import com.vaadin.flow.server.communication.IndexHtmlRequestListener;
 import java.io.IOException;
 import java.io.InputStream;
+import java.net.URL;
+import java.util.Enumeration;
+import java.util.Optional;
 import java.util.Properties;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * Service initialization listener that automatically applies a dynamic theme.
@@ -19,23 +24,51 @@
 @SuppressWarnings("serial")
 public class DynamicThemeInitializer implements VaadinServiceInitListener {
 
+  private static final Logger logger = LoggerFactory.getLogger(DynamicThemeInitializer.class);
+
+  private static final String PROPERTIES_PATH = "META-INF/dynamic-theme.properties";
+
   @Override
   public void serviceInit(ServiceInitEvent event) {
     if (DynamicTheme.isFeatureSupported()) {
-      try (InputStream in = getClass().getResourceAsStream("/META-INF/dynamic-theme.properties")) {
-        if (in != null) {
-          Properties props = new Properties();
-          props.load(in);
-          String themeName = props.getProperty("theme");
-          if (themeName != null) {
-            DynamicTheme theme = DynamicTheme.valueOf(themeName.trim());
+      try {
+        Enumeration<URL> resources = getClass().getClassLoader().getResources(PROPERTIES_PATH);
+        while (resources.hasMoreElements()) {
+          URL url = resources.nextElement();
+          String source = getSourceName(url);
+          readTheme(url).ifPresent(theme -> {
+            logger.info("Applying dynamic theme '{}' from {}", theme, source);
             event.addIndexHtmlRequestListener(theme::initialize);
-          }
+          });
         }
       } catch (IOException e) {
         throw new RuntimeException("Error reading dynamic-theme.properties", e);
       }
     }
   }
 
+  private Optional<DynamicTheme> readTheme(URL url) throws IOException {
+    try (InputStream in = url.openStream()) {
+      Properties props = new Properties();
+      props.load(in);
+      String themeName = props.getProperty("theme");
+      return Optional.ofNullable(themeName).map(String::trim).map(DynamicTheme::valueOf);
+    }
+  }
+
+  // Extracts a short, readable source name from the URL.
+  private String getSourceName(URL url) {
+    String path = url.getPath();
+    // JAR URLs look like: file:/path/to/file.jar!/META-INF/...
+    int jarSeparator = path.indexOf("!/");
+    if (jarSeparator > 0) {
+      path = path.substring(0, jarSeparator);
+      int lastSlash = path.lastIndexOf('/');
+      if (lastSlash >= 0) {
+        return path.substring(lastSlash + 1);
+      }
+    }
+    return url.toString();
+  }
+
 }